In our journey to develop better glazing outcomes, we embark on the intriguing process of glaze testing. In this experiment we are deliberately removing certain components from a glaze recipe to observe the distinct role ingredients play in the final outcome. Here’s how we go about this process:
We take our original glaze recipe and make up that glaze, we then repeat that process serval times leaving out one key ingredient from each new batch. This will help us understand the specific functions of these ingredients in a glaze.
The initial step is to assemble all the selected ingredients and blend them with a weighted amount of water. Mixing is crucial to ensure the ingredients are uniformly distributed and create a consistent glaze.
With our ingredients harmoniously combined, we are ready to proceed. We prepare a container with all the ingredients and use a high-speed mixer. This action homogenises the components, ensuring they are well-integrated.
The next stage involves dipping the test tiles into our glaze mixture. We partially submerge each one for four seconds, allowing the glaze to coat the surface evenly.
After the initial dip, we let the test tiles dry for a few minutes. Then, we opt for a second dip, focusing on the corner of the tiles, ensuring that they receive another four-second coating. This double-dipping approach allows us to gauge how the glaze builds up on the surface.
Welcome to the second part of glaze ingredient removal, in this part, we look at the results.
We kick things off with the first tile, which represents our glaze with all ingredients intact.
Moving on, we have a tile showcasing the glaze without the primary flux, feldspar. Take note of the structural and textural distinctions in this glaze.
The following tile demonstrates the glaze without the secondary flux. You’ll notice that it appears dry, indicating under-firing. It’s a clear reminder that both fluxes are essential for achieving the desired melt in our recipe.
With this tile we have removed the kaolin from the glaze recipe.
The next tile showcases a glaze devoid of silica. It has a matte finish and has crystal growth, lowering silica assists in turning a glaze matte from glossy.
We present a tile with the frit ingredient excluded. At cone 6 temperature, it’s evident that this glaze is significantly under-fired, underlining the importance of boron in a cone 6 glaze. It’s also important to note that this under fired glaze is not to be confused with a matte glaze.
Two subsequent tiles represent our glaze without rutile and the effect copper carb has on the green colour. And the absence of copper carbonate and the presence of rutile being responsible for the orange coloration in the glaze.
Our final tile without any colorants, showcases a glossy, transparent finish, highlighting the essence of colorants in colour development.
If you found this experiment intriguing and wish to delve deeper into the art of glaze chemistry, we recommend exploring online courses like “Understanding Glazes with Sue” and various offerings by Matt Katz at Ceramics Materials Workshop. These courses offer valuable insights into the world of ceramics and glaze composition.
